Carbon is one of the most important known elements and can be combined with oxygen, hydrogen, nitrogen and the like. Carbon has four known unique crystalline structures including diamond, graphite, fullerene and carbon nanotubes. In particular, carbon nanotubes refer to a helical tubular structure grown with a single wall or multi-wall, and commonly referred to as single-walled nanotubes (SWNTs), or multi-walled nanotubes (MWNTs), respectively. These types of structures are obtained by rolling a sheet formed of a plurality of hexagons. The sheet is formed by combining each carbon atom thereof with three neighboring carbon atoms to form a helical tube. Carbon nanotubes typically have a diameter in the order of a fraction of a nanometer to a few hundred nanometers.
A carbon nanotube is known to be useful for providing electron emission in a vacuum device, such as a field emission display, because of a higher current density than tip emitters. Additionally, the use of a carbon nanotube as an electron emitter has reduced the cost of vacuum devices, including the cost of a field emission display. The reduction in cost of the field emission display has been obtained with the carbon nanotube replacing other electron emitters (e.g., a Spindt tip), which generally have higher fabrication costs as compared to a carbon nanotube based electron emitter.
However, vacuum field emission devices are commonly plagued with emission currents that have leakage current flowing through a defect, e.g., particles, or nanotube grown unintentionally from a cathode to a gate electrode. In many electronic devices, these defects can be ‘blown-out’ by applying excessive voltage and current to the electrodes. This technique has been demonstrated in nanotube transistor research (not a vacuum field emission device) where excessive current has been used to destroy conductive nanotubes and nanotube walls in preference to semiconducting nanotubes. However, in the case of field emission devices which typically incorporate a ballast resistor in series with the emitter to limit destructive current to the nanotube, this technique is ineffective due to the current limiting ballast resistor.
A known method of improving uniformity of emission current reduces the length of longer emitters by causing a burn-in current to be emitted by the emitters with the longer emitters being reduced more than the shorter emitters due to the field created at the emitter tip. This known method reduces the effect of a ballast resistor by heating to a high temperature; however, this method does not reduce leakage or defects, and it cannot be performed in ambient air or at high pressure.
Accordingly, it is desirable to provide a fabrication process for reducing leakage current in a vacuum field emission display. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.